Gas burner flame arrester



Filed Oct. 29, 1947 M M. CANNON, JR., Erm.A

GAS BURNER FLAME ARRESTER Oct. 23, 1951 Patented Oct. 23, 1951 GAS BURNER FLAME ARRESTER Madison M. Cannon, Jr., West Hartford, and John S. Light, Sinisbury, Conn., assignors to Emhart Manufacturing Company, a corporation of Delaware Application ctober 29, 1947, Serial No. 782,754

This invention relates to improvements in flame airestors and it consists in the combinations, constructions and arrangements herein described and claimed.

An object of the invention is to provide a flame arrestor which will be effective to arrest flame close to a burner nozzle when conditions arise which tend to cause such a flame to flash back from the burner nozzle in a gaseous fuel supply line.

A further object of the invention is to provide a llame arrestor of a unitary character which is adapted to be operatively positioned in a gaseous fuel sup-ply line close to a burner nozzle that is being supplied with gaseous fuel by that line so as to prevent flash back of flame in the line without offering any substantial obstruction to the flow of the gaseous fuel to the nozzle.

A further and more specific object of the invention is to provide a flame arrestor having a core formed to provide numerous small passages extending therethrough and positioned in a gaseous fuel line as close to a burner nozzle that is being supplied with gaseous fuel from that line as is physically possible without causing any serious restriction of flow of gaseous fuel from the core passages into the burner nozzle.

To attain the foregoing and other objects of the invention, a straight section of a gaseous fuel supply pipe containing our arrestor and a holder for a burner nozzle to be served by that fuel supply pipe may be combined so that the volume of a space that is provided between the downstream end of the arrestor core and the burner nozzle as required to allow desirable uniformity of flow of gaseous fuel from the core passages into the rear of the nozzle is kept to a minimum. This space is kept as small as possible so as to keep to a minimum the volume of fuel mixture which may explode therein when a flash back occurs and hence similarly to restrict the force and velocity tending to drive the flame back through the arrestor. A second important advantage of the structure which provides a space of minimum volume between the burner nozzle and the downstream end of the arrestor core is that flow of burnt gases resulting from a flash back and burning of gaseous fuel-air mixture on the downstream end of the arrestor core out through the nozzle is at a rate very much reduced from the normal for any given mixture pressure in the supply line, this because of the high temperature and volume of the burnt gases in this restricted space. Rate of flow and rate of release of heat from the burnt gases are so re- 4 Claims. (Cl. 158-412) duced that burning can occur on the downstream end of the arrestor core for many hours without damage to the equipment. In all installations containing flame arrestors of the prior art of which we have any knowledge, burnt gases resulting from a flash back have flow space in which to cool substantially before arriving at the nozzle and flow through the nozzle hence is not reduced in the manner or to the extent provided by our invention.

Other obJects and advantages of the invention hereinafter will be pointed out or will be obvious from the following description of a practical embodiment of the invention, as shown in the accompanying drawings, in which:

Fig. l is a view, mainly in vertical section and partly in side elevation, of a burner nozzle and its gaseous fuel supply line operatively applied to a burner block and equipped with the novel flame arrestor of the present invention; and

Fig. 2 is a relatively enlarged, partial transverse section of the core of the flame arrestor, substantially along the line 2-2 of Fig. 1.

In Fig. l, numeral l designates a refractory burner block which is provided with a burner port 2 having its outer end portion enlarged or counterbored as indicated at 2a to accommodate the inner end and part of the length of a burner nozzle 3. The burner block I is shown as being provided with an outer metallic face plate 4 uprising from a horizontal supporting plate 5 which in turn extends across and rests upon a veitically disposed supporting plate 6, the inner end portion, designated 5a, of tne plate 5, underlying an outer end portion 7 of the lower surface of the burner block. The parts d, 5 and 6 may constitute part of a metallic framework or casing of the furnace (not shown) or other heat-using structure of which the burner block I is a part.

The burner nozzle 3 is mounted in a holder 8 which is shown as being an internally threaded metallic ring surrounding the outer end portion of the nozzle, designated 3a, which is relatively enlarged and is screw threaded externally so that it may be screwed into the holder 8 until a sealing gasket 9 surrounding the outwardly projecting portion of the burner nozzle is compressed by a flange I0 on the outer end of the nozzle against the outer face of the nozzle holding ring The nozzle 3 may have a screwdriver slot lila, in its flanged outer end to facilitate mounting of the nozzle in its holder 8 or removal therefrom.

The nozzle holding ring 8 is located at the inner end of and is rigid with a straight tubular ascia-145 fromfthe nozzle, the flamearrestor will restrict any ame at the rear ofv the nozzle to the downstream end of the arrestor when the gas to air ratio-of the gaseous fuelv mixture andthe gaseous mixture pressure are within any ranges that are likely to be encountered in service. Experiments have shown that at loads requiring a burner pres- Sure in excess 'of 0.05 inchwater gauge, the flame would be retained indefinitely on the discharge side of they arrestor core. On several occasions, conditions have been such as to cause or allow vflame to ash back through the burner nozzle in an installation like that shown in Fig. 1 and, in each case, the llame has lbeen retained on the arrestor. On one occasion, it burned over a whole week endv on. thearrestor with no damage or back lire.

The space 31 between the downstream end of the arrestor core and the outer end of the burner nozzle connes any explosive force to less than enough to force the ame back through the arrestor faster than the arrestor can extract heat from the burning gas. The volume of the space between the arrestor core and the burner nozzle influences directly both the quantity of heat that must be absorbed by the arrestor and the pressure developed which in turn influences the velocity with which the hot gas is driven back through the arrestor. It is important that the sizev of this space. beA kept to a minimum consistent with maintaining the required uniformity of ow from the arrestor core passages into the burner nozzle. The concave curvature of the front end 44 of the arrestor core contributes to this result as the discharge ends of the core passages are thus located nearer to the inlet end of the burner nozzle as they are farther from the axial line of the core and burner nozzle. There is also the relation of the volume of the space to the cross-sectional area of the burner nozzle passage to be considered. In trial equipment embodying the invention substantially as hereinbcfore particularly described, the space 31 had a volume of approximately 1.8 cu. inches and the free cross-sectional area or exhaust area of the nozzle was approximately 0.3 sq. inch, the ratio of these parts thus being approximately 6 to 1. The core was approximately 6 inches long. This trial equipment was operated with advantageous results such as have in part been hereinbefore described. When the core was moved back from the burner an inch or more, thereby enlarging the intervening space, the effectiveness of the name arrestor was markedly reduced. Also, when the length of the arrestor was reduced to approximately 4 inches, the effectiveness of the device was reduced somewhat although some of the advantages of the invention as hereinbefore described were still retained. These dimensions of parts are given by way of examples and not as limitations on the invention as obviously component parts having various dimensions and proportions may be used in constructing and using flame arresting equipment without departing from the spirit and scope of our invention.

We do not wish to be limited to the details of the illustrative embodiment of the invention as many changes therein and modifications of such embodiment now be obvious to or readily occur to those skilled in the art.

We claim: 1. A unitary flame arrestor for a burner assembly comprising a burner nozzle, a gaseous fuel supply line including a straight tubular nal section next to the nozzle and a nozzle holding ring connecting the nozzle operatively with the adjacent end of the straight tubular final section and projecting radially inward beyond the latter, said arrestor comprising a tubular casing sluidable in the straight tubular final section of the fuel supply line against the inwardly projecting portion of the holding ring, an axial stemv within the casing and projecting rearwardly therefrom in the fuel supply line, a filler in the casing between the latter and said stem, said filler terminating rearwardly of the forward end of the casing and comprising a multitude of longitudinal passages extending therethroughl and distributed throughout the crosssectional area of the ller, said passages having wallsof good heat transmitting properties, diametrically disposed retainerstrips in saidcasing at the opposite ends of said filler, said strips being fastened intermediately to the stem and the rear strip being fastened at its ends to the casing, a coil spring on the rearwardly projecting portion of the stem against the rear retainer strip, and removable means bearing on the spring to compress it against the rear retainer strip'to yieldingly maintain the casing in place against the nozzle holding ring.

2. A flame arrestor for a burner assembly comprising a substantiallyl straight tubular burner nozzle having only an axial bore for the passage of gaseous fuel therethrough and a gaseous fuel supplyline including a straight tubular section having a bore of substantially uniform crosssection throughout itsY length and nozzle holding means at the downstream end of said tubu'- lar section supporting said nozzle in axially aligned cooperative relation to the tubular section, the bore of said tubular section being substantially larger in cross-section than the adjacent end of the bore of said nozzle, said arrestor comprising a core having a multitude of longitudinal passages extending therethrough so as to be distributed around the longitudinal axis and throughout the cross-section of the core, said core tting in the bore of the supply line tubular section closely enough to prevent ow of gas between said core and the surrounding wall of said tubular section of the supply line so as to conne flow of gaseous fuel through the portion of the tubular section occupied by said core to the longitudinal passages of the core, said core being positioned in the supply line tubular section so as to leave a small space therein between the downstream end of the core and the adjacent end of the bore of the nozzle and being formed at its downstream end so that the downstream ends of the longitudinal passages therethrough are relatively nearer to or farther from the plane of the adjacent end of the nozzle bore as such passages are radially farther from or nearer to the axis of said core, respectively, so as to permit approximate uniformity of flow from the several passages of the core into the nozzle.

3. A flame arrestor for a burner assembly comprising, in combination, a gaseous fuel supply line including a straight tubular final section and a tubular nozzle secured to the downstream end of said final section so as to constitute a concentric relatively reduced extension thereof, the internal cross-sectional area of said final section of the supply line being substantially greater than the internal cross-sectional area of the adjacent end of the nozzle, a core comprising a multitude of longitudinally extending passages distributed symmetrically around Vthe longitudinal axis thereof, a tubular casing in Whichl said core ts closely, said casing being positioned in said nal section of the supply Vline so as to leave a relatively small space between the downstream end of the core and the adjacent end of the nozzle, said casing having a gas flow preventing fit with the surrounding wall of the final section of the supply line so that al1 gaseous fuel passing through said final section must pass through the longitudinal passages vof said core to reach the relatively small space between the downstream end of the core and said nozzle, the downstream end of said core being concavely curved so that the distance of travel of gaseous fuel from the individual core passages through said small space into said nozzle is approximately the same for all core passages despite differences in their radial distance from the axis of the core. Y

4. A flame arrestor for a burner assembly comprising, in combination, a gaseous fuel supply line including a straight tubular final section and a tubular nozzle secured to the downstream end of said final section so as to constitute a concentric relatively reduced extension thereof, the internal cross-sectional area of said final section of the supply line being substantially greater than the internal cross-sectional area of the adjacent end of the nozzle', a core comprising a multitude of longitudinally extending passages distributed symmetrically around the longitudinal axis thereof, a tubular casing in which Said core ts closely, said casing being positioned in said nal section of the supply line so as to leave a relatively small space between the downstream end of the core and the adjacent end of the nozzle, said casing having a gas flow preventing fit with the surrounding wall of the final section of the supply line so that all gaseous fuel passing through said nal section must pass through the longitudinal passages of said core to reach the relatively small space between the downstream end of the core and said nozzle, said core also comprising an axial stem extending therethrough and retainer strips disposed diametrically of the core at the opposite ends thereof and fastened intermediately to said stem, the retainer strip at the upstream end of the core being fastened at its ends to the casing of said core and the retainer strip at the downstream end of the core being free at its ends from said casing.

MADISON M. CANNON, JR. JOHN S. LIGHT.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date '140,857 Hooker Oct. 6, 1903 1,420,405 Beler June 20, 1922 1,494,009 Napolitan May 13, 1924 1,839,655 Dobbins Jan. 5, 1932 2,403,188 McCollum July 2, 1946 FOREIGN PATENTS Number Country Date 263,335 Great Britain Dec. 30, 1926 

